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Service Selection (Mode Selection) Most important factors: –Dependability (on-time delivery). –Cost. –Safety. –Tracking. Different modes have different costs and characteristics. Lowest transportation cost is not always best.

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Shortest Path Problem Given: –A network with a specified origin and destination. –The distance (or travel time or cost) for each link. Determine the shortest path from the origin to the destination. Solution:Labeling algorithm (one of many) –Nodes are labeled as "solved" or "unsolved". –Solved = shortest path from the origin to that node is known.

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Shortest Path Labeling Algorithm 1. The origin is a solved node. All others are unsolved. 2. For each solved node, find the one unsolved node that is nearest and calculate the minimum total distance (origin to solved node + solved node to nearest unsolved node). 3. Make the unsolved node with the smallest total distance a solved node. 4. Repeat steps 2 and 3 until the destination is a solved node. 5. Trace the shortest path.

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Transportation Problem Given: –m origins (sources for product flows). –n destinations (sinks for product flows). –Supply at each origin. –Demand at each destination. –Shipping cost per unit of product from each origin to each destination. Determine the minimum total cost shipping pattern to satisfy demand. –We will solve using TRANLP module of LogWare.

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Transportation Problem In last problem total supply = total demand. –Each origin sends all it has. –Each destination receives all it demands. Other possibilities: –Total Supply > Total Demand Some origins will keep some of the supply. –Total Supply < Total Demand Some destinations will not receive all they demand.